Toys which have the facility to run down vertical surfaces are well known in the toy art.
GB No. 1402126 discloses a toy having a shell and a magnetic roller housed in the shell. The roller adheres to a vertical ferromagnetic surface and the weight of the shell and roller cause the toy to roll downwards, the magnet keeping in touch with the surface. The specification also envisages a roller which may be electrostatically charged by rubbing and so adhere to a surface that way.
GB No. 696660 also shows a falling toy utilising a magnetic roller to attach it to a vertical surface.
U.S. Pat. No. 3,810,515 uses a magnet or a powered fan forming a vacuum to hold the toy against a surface.
GB No. 716949 discloses a toy which uses a plurality of magnets or suction cups which are mounted on spokes of a wheel. A spring or weight causes the wheel to rotate, the suction cups sequentially sticking to and lifting off a surface to effect a walking action. The specification envisages the use of a sticky substance on the ends of the spokes in place of the suction cups.
These toys have the drawback that they are limited to use on ferromagnetic surfaces or that they are complicated and expensive to produce, utilising many parts.